"People ask me where I come from. It's very hard for them to understand the accent is coming from inside my head."

An MRI scan showed that two lesions had developed at the back of her brain.

Mrs Fox says a doctor at Invercargill Hospital told her those were the most likely cause of the change in her speech.

"It certainly surprised me.

"My family have grown used to it now but the worst thing is friends I haven't seen for a long time.

"If they ring up they don't believe it's me on the phone. My best friend from Christchurch hung up."

Despite her Welsh first name, Mrs Fox traces her ancestry to the Orkney Islands and England.

"My mother got the name Bronwyn from a book she was reading when she was pregnant with me."

After hearing Welsh rugby players being interviewed during their recent tour of New Zealand, she concluded her new accent is mainly Welsh.

Her husband Rex said a cleaning woman who visited the house had Welsh relatives and also thought the accent sounded Welsh.

"It doesn't worry us," he said. "In fact it can brighten up a boring day."

Foreign accent syndrome is a rare medical condition usually reported as a side-effect of severe brain injury resulting from trauma or stroke.

The condition was first described in 1907, and between 1941 and 2009 there had been only 60 recorded cases around the world.

Earlier this year Sarah Colville, a 35-year-old migraine sufferer from Devon, began speaking with a Chinese accent after suffering a particularly severe headache.

Another case emerged in 2006, when Linda Walker, 60, from Newcastle-upon-Tyne, found that after a stroke her Geordie accent had been replaced by something variously described as sounding Jamaican, French Canadian, Italian and Slovak.